1. Field of the Invention
The present invention relates to an automatic air conditioning system for automotive vehicles. Specifically to a system which is capable of controlling the discharge mode in response to the environmental conditions in an automotive vehicle, such as a cool-down state wherein an essentially large amount of conditioned air with a relatively low temperature is discharged from a discharge outlet into the vehicular cabin, a steady state wherein temperature in the vehicular cabin is essentially equal to a target cabin temperature (target room temperature) determined by a vehicle occupant, or a transient state between the cool-down state and the steady state.
2. Description of the Prior Disclosure
Recently, there have been proposed and developed various automatic air conditioning systems with a controller which controls the opening angle of doors, such as a switchable fresh/recirculation air intake door, an air mix door, a defroster door, a chest vent duct door, a foot vent duct door, or the like, and controls amount of air flowing through the evaporator of the air conditioning system in response to control signals from various sensors for detecting various physical quantities, such as ambient temperature, temperature in the vehicular cabin, magnitude of insolation or the like. In general, such an automatic air conditioning system controls the discharge outlets in two discharge modes to maintain comfortable conditions in the vehicular cabin. One such automatic air conditioning system has been disclosed in the Japanese Patent First Application (Tokkai Showa) No. 57-15008.
In such automatic air conditioning systems for automotive vehicles, front discharge outlets, such as a center vent and a side vent, are provided in the instrument panel mounted on the front wall of the vehicular cabin 7. Each front discharge outlet includes a louver with a plurality of fins. Each louver is associated with a discharge outlet actuator for actuating the fins thereof. In general, the fins of the louvers are operated in either a first discharge mode or a second discharge mode according to the movement of the actuator. In the first discharge mode, an essentially large amount of conditioned air flowing through the fins is concentratedly discharged from a front discharge outlet to the occupants of the front seats. On the other hand, in the second discharge mode, the conditioned air flowing through the fins is diffused to all regions within the vehicular cabin. The former mode will be hereinafter referred to as "concentrated discharge mode", while the latter will be referred to as "diffuse discharge mode". During a cool-down state, the occupants of the front seats in the vehicular cabin may quickly feel a cooling effect via the concentrated discharge mode control. When environmental conditions in the vehicular cabin transit from the cool-down state to the steady state, the air conditioning system can prevent excessive cooling via the diffuse discharge mode control.
However, actually, in a transition from the cool-down state to the steady state, the environmental conditions in the vehicular cabin vary momentarily according to the lowering of the cabin temperature or discharge air temperature from the discharge outlets. Usually, when the air conditioning system is continuously operated in the diffuse discharge mode, the occupants in the vehicular cabin lose feeling relative to a cooling effect. Therefore, the two discharge modes of prior art air conditioning systems cannot provide sufficiently comfortable conditions in the vehicular cabin or optimum feeling of the occupants. In other words, a smooth transition between the cool-down state and the steady state cannot be satisfied sufficiently.